As electronic technology advances, digital systems are being produced that operate at higher and higher clock frequencies. In addition, more circuitry and components are being integrated into smaller volumes. While these advances are beneficial because of the product features they make possible, high-frequency switching usually causes unwanted radiation of electromagnetic energy. This results in EMI. Most countries strictly regulate the amount of EMI that a given electronic device is allowed to generate. Therefore, new and better methods for reducing EMI produced by electronic devices are always desirable.
A particular point of concern in the reduction of EMI caused by such devices is EMI leakage at joints and at openings in the device enclosure. For example, EMI has been found to leak through areas in the enclosure where components such as connectors are mounted for external access. Consequently, various EMI gaskets have been designed for reducing EMI leakage around connectors that are mounted in an opening in a device enclosure.
One such EMI gasket is disclosed in U.S. Pat. No. 5,317,105, issued to William F. Weber May 31, 1994, and assigned to Alcatel Network Systems, Inc. (hereinafter "Weber"). Weber discloses a gasket formed from a conductive gasket plate having a central slot large enough to allow a connector receptacle to pass through it. Deflected teeth, formed from the gasket plate material on two edges of the slot, protrude away from the plane of the gasket plate on one side of the gasket plate and engage a connector inserted into the connector receptacle.
Another EMI gasket is disclosed in U.S. Pat. No. 5,204,496, issued to Steven G. Boulay, et al. Apr. 20, 1993, and assigned to Digital Equipment Corporation (hereinafter "Boulay"). Like Weber, Boulay discloses using a conductive gasket plate having a central slot therein. Unlike the Weber gasket, however, the Boulay gasket does not have teeth on two edges of the slot. Instead, Boulay discloses a series of "turned-out" comers disposed along two of the outside edges of the gasket plate. The turned-out corners all protrude away from the plane of the gasket plate on one side of the gasket plate and engage a circuit card face plate on the inside of the device enclosure. Two u-shaped mounting channels are formed from the gasket material on the side of the gasket opposite the turned-out corners. The mounting channels secure the EMI gasket to the device enclosure by engaging opposing edges of a hole in the enclosure.
While these EMI gasket designs provide some reduction of EMI leakage for particular component arrangements and device enclosures, it is an object of the present invention to provide an improved EMI gasket and component arrangement having enhanced EMI leakage reduction characteristics.